I like this approach very much, and it fits in nicely with
the use of rdf:value as a mechanism for scoping, as used
by alot of folks (including myself and the Adobe XMP folks)
C.f.
http://www.jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0212&L=dc-architecture&T=0&F=&S=&P=726
It captures the DC concept of "dumbing down" very well, and in
a formal manner, and provides all RDF processors with a consistent
interpretation of rdf:value in terms of such simplification.
I support Pat in inserting the proposed semantics for rdf:value
into the MT and for Frank to massage the verbage in the Primer
accordingly.
It does not appear to break any current usage of rdf:value but
rather captures the intersection of meaning shared by all of
the current uses of rdf:value in various applications.
Patrick
[Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com]
----- Original Message -----
From: "ext pat hayes" <phayes@ai.uwf.edu>
To: <w3c-rdfcore-wg@w3.org>
Sent: 09 December, 2002 06:59
Subject: handling rdf:value
>
> After reading Franks section in the primer more carefully, I would
> like to make the following suggestion for how to handle rdf:value,
> which I think codifies the intent rather better than any other idea
> we've had so far. I've rewritten Frank's section 4.2 along these
> lines in the version at
> http://www.coginst.uwf.edu/~phayes/RDF-Primer-modified.html, but of
> course this rewrite is only OK if people agree to the treatment.
>
> -------
>
> Frank characterizes the typical use of rdf:value as a way to indicate
> a 'primary' value of a multi-arity relation. (Note, this is not at
> all the same notion as a primary field in a DB.) That is, when R is a
> more-than-binary relation, but can be abbreviated usefully as a
> binary one by ignoring some of its arguments, then the rdf:value is
> the argument that should not be ignored. In cases like this, we can
> typically think of the binary form as an abbreviation or summary of
> the longer formulation, where some detail has been omitted or
> suppressed.
>
> I think that this very nicely captures the intended range of uses for
> rdf:value, and doesn't get it confused with issues like
> distinguishing dimensions from values or textual forms from real
> values, which I had often gotten it confused with. But it suggests
> the following slightly modified treatment.
>
> The *strictly correct* use of rdf:value is to do *exactly* the above,
> and no more; ie to say, when a relation with more than two arguments
> is described by having a structured value which itself has the other
> arguments as values, which one of those arguments can be
> appropriately used as the single argument when the n-ary relation is
> abbreviated or summarized as a binary relation, ie a simple property.
> For example, using the address example that Frank gives:
>
> exstaff:85740 exterms:address _:johnaddress .
> _:johnaddress exterms:street "1501 Grant Avenue" .
> _:johnaddress exterms:city "Bedford" .
> _:johnaddress exterms:state "Massachusetts" .
> _:johnaddress exterms:Zip "01730" .
>
> an appropriate use of rdf:value here might be to add:
>
> exstaff:85740 exterms:address _:johnaddress .
> _:johnaddress exterms:street "1501 Grant Avenue" .
> _:johnaddress exterms:city "Bedford" .
> _:johnaddress exterms:state "Massachusetts" .
> _:johnaddress exterms:Zip "01730" .
> _:johnaddress rdf:value "01730" .
>
> which would say that the way to succinctly abbreviate this in binary
> form would be to just use the Zip code as the address, ie that it is
> correct, even if less informative, to also write:
>
> exstaff:85740 ex:terms:address "01730" .
>
> Now, of course, this kind of strictly correct usage means that one
> has to say the value twice; once with its correct attaching property
> and once again with rdf:value; and so users may wish to abbreviate
> this by omitting the 'correct' property, and leaving it implicit; but
> that strategy is inherently risky, as the intended meaning of
> rdf:value is now contextual and liable to be misunderstood if taken
> in isolation. So, caution.
>
> On this view, the 'proper' way to write the kilogram example would be
>
> aaa weightIs _:x .
> _:x ex:quantity "24" .
> _:x rdf:value "24"
> _:x ex:units ex:kilograms .
>
> And omitting the second triple is an obvious economizing strategy,
> but users are cautioned that it has its risks.
>
> -----
>
> If people like this idea than it could be captured formally as a RDF
> semantic condition corresponding to the inference rule:
>
> aaa ppp bbb .
> bbb rdf:value ccc .
> -->
> aaa ppp ccc .
>
> for any property ppp. This would fit very naturally into
> rdf-entailment. But as this goes beyond
> http://www.w3.org/2000/03/rdf-tracking/#rdfms-replace-value.
> I hereby REQUEST feedback from the WG before inserting it into the
> MT. If people think it should be there then I can put it in one
> evening this week. All the proofs and so on are transparent to this
> addition.
>
> Pat
>
> PS. BTW, this account allow you to use rdf:value for more than one of
> the properties, and the semantics then would be that *either* of them
> could be correctly used as the abbreviating property, eg if you also
> said that the city was an rdf:value, then it would be correct to use
> either the zip code or the city as the value of the simple address
> property instead of the structured value encoding all the aspects of
> the address.
>
>
> --
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